Health Centres - Co-trimoxazole tablets
How does it work?
There are two active compounds in co-trimoxazole, trimethoprim and sulfamethoxazole (previously spelt sulphamethoxazole in the UK). Sulfamethoxazole belongs to the sulphonamide group of antibiotics. Trimethoprim and sulfamethoxazole both work inside the bacterial cell, where they stop the manufacture of a substance called folic acid (folate). Folic acid is necessary for the production of genetic material (DNA). Without the production of DNA the bacteria is not able to reproduce, and the spread of the infection is stopped (a bacteriostatic effect).
What is it used for?
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Chronic bronchitis
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Ear infections
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Infection of the bladder or tubes that pass urine
- Prevention of pneumonia caused by the bacterium pneumocystis carinii (PCP). The risk of this infection is increased in patients with decreased immune system function.
- Treatment of pneumonia caused by the bacterium pneumocystis carinii (PCP)
Warning!
- You should ensure that you drink plenty of fluids while receiving treatment with this medicine.
- People taking this medicine should have regular blood tests.
Use with caution in
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Asthma
- Blood disorders
- Decreased kidney function
- Decreased liver function
- Elderly people
- Infants under 6 weeks of age
- Lack of the enzyme G6PD in the blood (G6PD deficiency)
Not to be used in
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Kidney failure
- Life long inherited blood diseases which can cause a variety of symptoms, including mental health problems (porphyrias)
- Liver failure
This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
Pregnancy and Breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- This medicine should not be used during pregnancy as it may be harmful to the unborn baby. Seek medical advice from your doctor.
- This medicine passes into breast milk. Seek medical advice from your doctor before using this medicine during breastfeeding.
Label warnings
- Take at regular intervals. Complete the prescribed course unless otherwise directed.

